The Distinct Build-Up Of Dense And Normal Massive Passive Galaxies In Vipers

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2017

Publication Year

2020-07-24T13:52:29Z

Acceptance in OA@INAF

The Distinct Build-Up Of Dense And Normal Massive Passive Galaxies In Vipers

Title

GARGIULO, ADRIANA; Vipers Team

Authors

10.5281/zenodo.807380

DOI

http://hdl.handle.net/20.500.12386/26631

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The distinct build up of

dense and normal

passive galaxies in VIPERS

ADRIANA GARGIULO & THE VIPERS TEAM

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• Why studying massive (M_star > 1011_M

sun) passive galaxies (MPGs)

• The evolution of the number density and of the stellar population ages of MPGs at 0.5 < z <1.0 • The impact of the environment on the mass assembly history of MPGs

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Most of the stellar mass in galaxies today resides in massive passive systems

(e.g. Renzini 2006).

Still unclear WHEN & WHERE the stars in massive galaxies were formed

THE ‘MERGER’ (EX SITU) HYPOTHESIS

In a ΛCDM Universe the assembly of massive galaxies is dominated by the (dry) accretion

of stars formed in other galaxies

(e.g. Naab+ 2009; Qu+ 2017; Rodriguez-Gomez+ 2016; Gabor&Davè 2012; Lackner+ 2012 / e.g.

Robertson+ 2006; Cox+ 2006; Pipino+ 2008)

THE IN SITU HYPOTHESIS

Stars in massime galaxies come from in situ star formation (untill an event – e.g.

AGN feedback, halo shock, disc fragmantation – does not stop it)

(Genzel+ 2008, 2011; Förster Schreiber+ 2011; Tacconi+ 2013; Wuyts+ 2013)

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STRUCTURAL PROPERTIES OF LOCAL AND HIGH-Z MPGs

THE EX SITU HYPOTHESIS vs. THE IN SITU HYPOTHESIS Do we need a combination of these?

Evolutionary models have to reproduce MPGs properties as the size-mass relation and its evolution with time

Belli et al. 2014

At fixed stellar mass

• local MPGs have dimensions that vary up to an order of magnitude;

• high-z (z ~ 2) MPGs are smaller than local MPGs by a factor ~ 5

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STRUCTURAL PROPERTIES OF LOCAL AND HIGH-Z MPGs

THE EX SITU HYPOTHESIS vs. THE IN SITU HYPOTHESIS Do we need a combination of these?

Evolutionary models have to reproduce MPGs properties as the size-mass relation and its evolution with time

Given the mean stellar mass density Σ = M_*/(2 π R_e2₎

on average

high – z MPGs were denser than local MPGs

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THE OPEN QUESTIONS

• Why, at fixed stellar mass, the typical dimension of a MPGs varies up to an order of magnitude?

• Have dense and less dense local MPGs different stellar mass assembly history?

In which way was build up the population of local MPGs?

TO FIND THE ANSWER WE STUDIED:

1. the evolution of the number density of MPGs as a function of Σ

2. the evolution of the stellar population ages of MPGs as a function of Σ 3. the correlation of Σ and the local environment

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VIMOS PUBLIC EXTRAGALACTIC REDSHIFT SURVEY

VIPERS IN A NUTSHELL

ESO LARGE PROGRAM (PI: L. Guzzo) SPECTRA :

LRR grism (R = 200)  [5500 – 9500] A  Δz = 0.00047(1 + z) TARGET SAMPLE :

• i(AB) < 22.5 on the CFHTLS Wide W1 and W4 fields • ugri colour pre-selection  z > 0.5

VOLUME :

5 x 107 _h-3 _Mpc3 _{- comparable to 2DF but at redshift ~ 1}

AREA :

24 sq. dg (~ 16 without gaps) – 40% sampling rate PHOTOMETRY : NUV, u, g, r, i, z, K ++ (Moutard et al. 2016)

Now available at

http://vipers.inaf.it/

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THE VIPERS SAMPLE OF MPGs

The selection criteria:

•

2 ≤ z_flag ≤ 9.0

•

0.5 ≤ z ≤ 1.0

•

(NUV – r) vs (r –K)

•

M_star ≥ 1011 _M

sun (Cha IMF)

~2000 MPGs at 0.5 < z < 1.0 with z-spec

To derive Σ: Re in i band for galaxies at z ≥ 0.8

Re r band for galaxies at z < 0.8 ~ U band rest frame over the whole redshift range

Davidzon et al. 2013, 2016

For structural parameters in VIPERS see Krywult+ 2016, δR_e < 10%

High-Σ MPGs  Σ > 2000M_sun pc-2 _--- _{Intermediate- Σ MPGs  1000 < Σ ≤ 2000M}

sun pc-2 Low- Σ MPGs  Σ ≤ 1000M_sun pc-2

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THE EVOLUTION OF THE NUMBER DENSITY OF MPGs

AS A FUNCTION OF Z AND Σ

Number densities fully corrected for incompleteness

Errors take into account the Poisson fluctuations and the error on Re The evolution of the number densities

depends on Σ :

the lower the Σ, the faster the evolution From z = 1.0  z = 0.5: Increase factor: Total : ~ 2.5 High Σ : ~ 1.2 Int Σ : ~ 1.7 Low Σ : ~ 4.2

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THE EVOLUTION OF THE STELLAR POPULATION AGES OF MPGs

AS A FUNCTION OF Z AND Σ

Compact MPGs

The evolution both of the number density and of the mean age of dense MPGs show that they passively evolve

The approach:

1. ages derived from the SED fitting  Mean Age/Z/Tau (z, Σ); 2. Mean Age/Z/Tau (z, Σ) + BC03 models  D4000_SED (z, Σ); 3. D4000_SED (z, Σ) vs D4000_obs(z, Σ)

MEAN AGE FROM SED

MEAN OBSERVED D4000n

MEAN SED D4000n

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THE EVOLUTION OF THE STELLAR POPULATION AGES OF MPGs

AS A FUNCTION OF Z AND Σ

The evolution of the number density and of the mean age of less dense MPGs show that a significant fraction of NEW and YOUNGER MPGs should

appear at later epoch

Dense MPGs are older than less dense ones

(see also, e.g. , Poggianti+ 2013, Saracco+ 2010, Williams+ 2016, Fagioli+ 2016 at smaller M_star) Less dense MPGs

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CONCLUSIONS - 1

From redshift 1.0 to 0.5

the population of MPGs (mainly) grows bottom – up:

on top of the population of denser MPGs already in place at z ~ 1.0, new, younger, and larger MPGs appear at lower z

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CONCLUSIONS - 1

From redshift 1.0 to 0.5

the population of MPGs (mainly) grows bottom – up:

on top of the population of denser MPGs already in place at z ~ 1.0, new, younger, and larger MPGs appear at lower z

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The increase in number density of MPGs at z < 0.8 is totally accounted for by the

decrease in number density of active massive galaxies

Active massive galaxies most likely progenitors of MPGs

(see, e.g. Lilly & Carollo 2016).

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THE PROGENITORS OF (LESS DENSE) MPGs

dry mergers

Increase in the number density

due to other MPGs formation channels, e.g. dry mergers

Any other channel of MPGs formation

different from the quenching of active massive galaxies will result in an overabundance

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THE IMPACT OF THE ENVIRONMENT ON Σ

Dry mergers increase the galaxy size + merger activity enhanced in higher density regions

Larger galaxies in denser environment

δ = [ρ (ra, dec,z)/ρ (z) ] - 1

5° neigh.

2000 km/s

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THE IMPACT OF THE STELLAR MASS DISTRIBUTION

ON THE δ vs. Σ CORRELATION

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THE IMPACT OF THE STELLAR MASS DISTRIBUTION

ON THE δ vs. Σ CORRELATION

Positive corralation bewteen M_star and R_e& δ

Spurious positive correlation between δ and Σ

Mass-matched samples

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(PRELIMINARY) RESULTS

At M_star < 2*1011_M

sun we do not find

significative evidence of a trend between δ and Σ

Low-Σ MPGs

High-Σ MPGs

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(PRELIMINARY) RESULTS

Lack(abundance) of compact(less dense) verymassive PGs

in the densest regions:

1. High density regions

prevent(favor) the formation of compact(less dense) MPGs with

M_star > 2*1011_M sun

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(PRELIMINARY) RESULTS

2. Or compact MPGs with M_star > 2*1011_M

sun disappear from high- δ

regions ( less dense) t = to

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(PRELIMINARY) RESULTS

2. Or compact MPGs with M_star > 2*1011_M

sun disappear from high- δ

regions ( less dense) t = t1 > to

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(PRELIMINARY) RESULTS

Δn

BCGs ‘creation’?

The drop in the number of compact MPGs in the highest desnity regions

=

to the increase in the number of less dense MPGs in the highest density

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(PRELIMINARY) RESULTS

Δn

BCGs ‘creation’?

Thank you!

The drop in the number of compact MPGs in the highest desnity regions

=

to the increase in the number of less dense MPGs in the highest density